Method and apparatus for laying a bituminous road mat



Jan. 1,1963 P. PIZZAROTTI ETAL METHOD AND APPARATUS FOR LAYING ABITUMINOUS ROAD MAT Filed Dec. 21, 1959 2 Sheets-Sheet 1 inventors Wen,Win/0th- Camel! Arlflvnucai 4nd Gianni; Lanni Afborny Jan. 1, 1963 P.PIZZAROTTI ET AL 3,071,049

METHOD AND APPARATUS FOR LAYING A BITUMINOUS ROAD MAT A Cfarnzy3,071,049 METHOD AND APPARATUS FOR LAYING A BITUMHNUUS ROAD MAT PietroPizzarotti, Carnillo Antonucci, and Giovanni Leoncini, Parma, Italy,assignors to Impresa Pizzarotti &

C.S.r.l., Parma, Italy, a company of Italy Filed Dec. 21, 1959, Ser. No.860,877 6 Claims. (Cl. 94-46) In our copending application Serial No.727,684 a method had been described for obtaining vertical curves inlaying of bituminous mats with asphalt spreading finishing machines.

For curves of very great radius (for instance 10,000 metres) it wouldhave been necessary, with the method and apparatus of our copendingapplication mentioned above, to proceed with successive levels (spacedby about 20 metres apart) each of which represented a secant line of anarc of the vertical curve to be reproduced on the ground. In ortherwords, one would have had to substi tute, for the vertical curve, thepolygonal of its secants and, therefore, to obtain satisfactoryaccuracy, it would have been necessary to provide the levels as close aspossible to one another, thereby unduly mulitplying the number ofsetting operations for the topographical control instruments and theguide, beyond limits acceptable in practice.

It is an object of the present application to provide a method forobtaining in a continuous manner curves of vertical profile withbituminous mats on roads, by means of road finishing machines. Anotherobject of the present application is to provide a method for obtainingvertical curves with the highest fidelity to the profile of design.

It is a further object of the present application to provide apparatussuitable for the practicing of the method.

Other objects and advantages of the invention will appear from thefollowing detailed description of some preferred embodiments of themethod and of the apparatus for practicing it.

For practicing the method, one must prepare a graph of the verticalcurve desired, that is, a graph representing the path of a mat to belaid on a given arcuate portion of a vertically curved road, and whereinthe abscissae are proportional to the progressive distances over whichthe finishing machine moves, computed on the chord of the arc of curveto be obtained, and the ordinates are equal to the distances of everyrespective point of the curve from the chord. Since the absolute valuesof the progressive distances are comparatively great with respect tothose of the distances of the points of the curve from the chord, itwill be convenient that the abscissae should be a certain fraction ofthe true progressive distances, while the ordinates will be of naturalmagnitude (scale 1:1).

According to a preferred embodiment, the graph representing the verticalcurve is supported on a cylinder rotatable around a vertical axis; and avery limited portion of the grap on said cylinder is collimated by atopographic instrument. The rotation of the cylinder around its axis iscontrolled by a wheel, rigid with the spreading machine, rolling on theground, so that to an arc of rotation of the cylinder there correspondsa determined portion of road on the. ground. The cylinder is rigid withthe members for adjusting the thickness of the mat laid down by thespreading machine whence the collimation of the successive points of thegraph must be obtained by displacing said thickness control membersvertically. That is obtained by means of a remote control as will bedescribed more in detail hereinafter.

According to another embodiment, the reference line is a beam of lightgenerated by a source placed in front of the spreading machine; and saidpoint of reference is a means responsive to a gradient of illuminationplaced 3,071,049 Patented Jan. 1, 1963 on said thickness control membersand limitedly movable with respect thereto in vertical direction and thevertical strokes whereof are made to vary according to a continuousfunction geometrically similar to the level to be obtained. In practice,a cylindrical cam is used, on the periphery of which there is securedthe graph of the curve to be obtained, and a pair of photoelectric cellsare provided which have vertical strokes that are controlled by saidcam. The frame supporting the cam and the cells is rigid with themembers for adjusting the thickness with which the spreading machine isequipped. A source of light external to the machine projects a beam oflight rays onto the two cells which are contiguous and verticallysuperimposed and every gradient of illumination of the two cells causesthe actuation of a servomotor which lifts or lowers the members foradjusting the thickness of the bituminous mat until the gradient ofillumination between the two cells becomes nil.

The invention will now be described in detail with reference to theaccompanying drawings which illustrate some preferred embodiments of themethod and of the apparatus:

FIG. 1 represents a first embodiment of the method and relatedapparatus; FIG. 2 represents a second embodiment of the method and theapparatus adapted to practice it; and FIG. 3 is a detailed view of therotatable cylinder which carries the graph in the embodiment illustratedin FIG. 1.

Now with reference to the accompanying drawings, FIG. 1 represents aspreading machine 10, equipped with a plate 11 which is mounted on thelower end of a vertically adjustable shaft s. Shaft s is externallythreaded along at least a portion of its length and threads through aprojection s on the machine frame so that rotation of the shaft shiftsplate 11 vertically. Plate 11 is thus used for adjusting the thickness,while it is laying a bituminous mat. The vertical curvature of the roadhas been somewhat exaggerated in the drawing in order to make the representation clearer. To the plate 11 is rigidly fixed a vertical upright15 supporting a generally rectangular frame 17, which in its frontportion has a slit 18. The upright 15 supports a rotatable cylinder 16on which there is wound a paper bearing the graph 19 of the curvedprofile to be traced. The abscissae of the graph, as already said,represent the distances covered by the spreading machine 10 as itproceeds, while the ordinates are equal to the vertical distances of thepoints of the profile to be traced, measured from the horizontal chordof the arc of the road. The slit 18 in the frame 17 permits collimatinga limited portion 19' (virtually point-shaped) of the graph 19. Thecylinder 16 is adapted to be rotated around its own vertical axis, andsaid movement is of an amplitude proportional to the distances coveredby the spreading machine 10: in fact to the spreading machine 10 thereis atfixed a wheel R rolling on the ground by friction; and the movementof R, through a flexible shaft A, is transmitted to the cylinder 16 byway of reduction gears designated generally at 16' in the drawing.

It is apparent that, by selecting conveniently the radius of R and theratios of transmission, the rotation of the cylinder 16 can take placein a certain ratio with respect to the speed of rotation of R.

On the spreading machine there is also a radioreceiver set 13 providedwith an antenna 14. The set 13 is electrically connected by conventionalmeans of the type disclosed, for instance, in our above-noted copendingapplication, with a ser-vomotor 12. (reversible) and the latter, throughfor instance a mechanism, such as the helical worm gear Wheel W and itsmating worm, rotates shaft s in one direction or the other and therebycauses the lifting or lowering of the plate 11.

In front of the spreading machine, at a distance corresponding to thelength of the arc of curve to be obtained (for instance 150 m.), thereis provided a sighting telescope 22, the sighting line of which shouldalways be kept in collimation with the portion 19 of the graph 19visible in the slit 18.

A radio transmitter set 21, equipped with an antenna 20 and controlledby a push-button key-board 23, emits pulses which are received by 13through the antenna 14. The key-board 23 is provided with twopush-buttons so as to enable sending pulses of opposed signscorresponding then to the two directions of rotation of the motor 12and, therefore, to the lifting or lowering of 11. The push buttoncontrol transmitter set 21 is adapted to control motor 13 throughconventional means such as the type illustrated in FIGS. 7 and 8 of ourabove-noted copending application. So when the operator in sighting withthe telescope 22 secs, while the spreading machine 10 progresses, thatthe portion 19' visible at a certain instant through the slit 18 is notin collimation with the sighting line of 22, he promptly intervenes bymeans of the key-board 23 by emitting pulses (positive or negative)until the collimation relationship is re-established. In that Way theideal profile 19 will be reproduced with great accuracy and incontinuous manner, while avoiding repeated setting of topographicalinstruments: in other words, the curve 19 is reproduced on the groundpoint by point and not as a polygonal of its secants.

The internal circuits of the radiotransmitter and radioreceiver setshave not been described because any known types may be adopted for thepurpose indicated.

FIGURE 2 describes another embodiment of the invention: also in thisfigure, the curvature of the road profile in the vertical plane has beenconsiderably exaggerated in order to show it clearly.

In FIG. 2 is visible a spreading machine equipped with a plate 11 foradjusting the thickness: the vertical movements of the plate 11 arecontrolled by a reversible motor 12', through the helical gear W and amating worm. The worm is driven by said motor 12'. The helical gear isintegral with an internally-threaded nut that engages the threadedportion of the shaft s to adjust the plate 11 vertically.

To the plate 11' there is rigidly connected an upright 25 supporting aframe 25: hence to the vertical displacements of the frame 25' withrespect to the sight line there correspond displacements of equalamplitude and direction of the plate 11' and viceversa. The frame 25'supports, as visible in FIGURE 2, the cylindrical cam 31 one end face ofwhich reproduces the desired profile. The cylindrical cam 31 can turnaround its own vertical axis.

The movement of rotation of the cam 31 is derived from the wheel R,through the flexible shaft A and a train of reducing gears in a mannerperfectly analogous to What has been said in the description of FIG. 1.

The rotation of the cam 31 controls the vertical movement in onedirection or in the other direction of the slidable rod 32 which canslide in the stirrups 26 and 27 fixed to the frame 25'. In FIG. 2 it isvisible that the slidable rod carries two photoelectric cells 33 and 34contigous and vertically superimposed to each other.

A source of light, for instance a projector 29 fed by a battery 30,projects a beam of rays of light, the axis of which is clearly visiblein FIG. 2, onto the cells 33 and 34. For the preliminary sighting of thesource of light 29, a telescope such as 28 is useful.

The cells 33 and 34 are connected with a circuit 24, 24, a control group13' and a reversible servomotor '12 in a manner similar to thatdisclosed. in FIGS. 2 to of our above-noted copending application.

As already said, the gradient of illumination between the cells 33 and34 should be nil while the machine It)" progresses and the cam 31 turns:this is the essential condition which, alone, warrants the truereproduction on the field, of the vertical curve to be obtained. In thiscase in fact the point of reference is the small space between the twophotoelectric cells and so, when the beam of light is symmetricallyarranged with respect to them, the gradient of illumination is nil andthe motor 12' does not turn; while if there is a gradient ofillumination between the cells, there arises an electromotive force inthe circuit 24, 24', 13, of positive or negative sign according towhether the one or the other of the cells is more intensivelyilluminated. In FIGURE 2 the beam of light (of which only the axis isvisible) has been represented as incident completely upon the lower cell3 4: this is obviously a limit condition represented in the figure inexaggerated manner. In practice in fact the axis of the beam of lightmust fall between the two cells and the deviations are compensated bythe actuation of the servomotor 12'. In the position of FIG. 2, themedial axis of interspace between the two photoelectric cells is muchhigher than it should be (namely in correct position it ought tocorrespond to the axis of beam of light); hence the plate 11' should belowered until the gradient of illumination between the cells becomes nilagain. Hence it will suflice that the sign of the electromotive forcedue to the gradient of illumination is made conveniently to be in accordwith the direction of rotation of the motor 12': this is easilyobtainable in ordinary electrotechnics. When the grad ient ofillumination is nil, therein zero electromotive force in the circuit 24,24, 13' and, therefore, the motor 12' stops: the machine 10' isfollowing accurately the profile commanded.

We claim:

1. A method for laying a road mat on a vertically curved road bed with aroad machine which is equipped .with a road mat leveling member and withmeans for adjusting said member vertically to control the thickness ofsaid mat and the location of its upper surface, said method comprisingproviding an optical line of reference extending parallel to the chordof an arcuate portion of said road bed, moving a controlling member,which is mounted on said leveling member and which has a controllingcurved surface, the ordinates of which represent the vertical contour ofsaid arcuate portion, past a vertical plane containing said referenceline at a rate proportional to the rate of travel of the machine alongthe road, and moving said leveling member up or down as required tocause successive points on said curved surface to lie on said referenceline as the machine travels along the road.

2. A method for laying a road mat as claimed in claim 1, wherein saidoptical reference line is the sight line of a topographic instrumentplaced in front of the machine, said point is on a graph which isgeometrically proportioned to the grade level desired, and which ismoved in proportion to the rate of travel of the machine along the road.

3. A method for laying a road mat as claimed in claim 1 wherein twovertically spaced light-responsive elements are provided which areconnected to said curved surface on said controlling member to be movedvertically thereby in response to the shape of said curved surface, saidoptical reference line is a beam of light generated by a source placedin front of the machine, and moving said light-responsive elementsvertically in proportion to change in vertical curvature of the road asthe machine travels over the road.

4. A machine for laying a road mat according to a desired grade,comprising a vertically movable road leveling member, control meansmounted on said member for vertical movement therewith and including acylinder mounted to rotate on a vertical axis and having a curve thereonin proportion to the desired grade shape, means for rotating saidcylinder as said machine moves along the road in proportion to the rateof travel of the machine therealong, and remotely-controlled means foradjusting said leveling member to maintain the curve constantly in apredetermined relation to an optical reference line.

5. A machine for laying a road mat according to a desired grade,comprising a road leveling member, control means mounted on said memberfor movement therewith and including a cylinder mounted to rotate on avertical axis and having a graph thereon proportioned to the grade curvedesired, means for rotating said cylinder as said machine moves alongthe road and in proportion to the rate of travel of said machinetherealong, said cylinderrotating means including a roller having ahorizontal axis and mounted to roll on the road during the travel of themachine, a screen positioned in front of said cylinder which has anarrow vertical slit therein, so that the portion of said graph whichregisters at any time through said slit can be viewed by a topographicalinstrument,

which is placed in front of the machine and whose line of sightconstitutes an optical reference line, and remotelycontrolled means foradjusting said leveling member to maintain said portion of said graphcoincident with said reference line.

6. A machine for laying a road mat according to a desired grade,comprising a road leveling member, control means mounted on said memberfor movement therewith and including a rotary cam whose active surfacehas an active shape proportioned to the grade shape of the road mat tobe laid, a carrier, a pair of vertically superimposed photoelectriccells mounted on said carrier, means connecting said cam to said carrierto move said cells vertically upon rotation of said cam, means forrotating said earn as said machine travels over the road and inproportion to its rate of travel, and remotely-controlled means foradjusting said leveling member, said remotely-controlled means beingoperative to move said carrier vertically as said vehicle travels, sothat equal amounts of light fall on both said cells from a light beamcoming from a source of light which is placed in front of the vehicle,said beam constituting an optical reference line.

References Cited in the file of this patent UNITED STATES PATENTS2,295,519 Millikin Sept. 8, 1942 2,796,685 Bensinger June 25, 19572,864,452 Guntert Dec. 16, 1958 2,916,836 Stewart Dec. 15, 19592,922,345 Mentes Jan. 26, 1960 FOREIGN PATENTS 54,126 France June 2,1947

1. A METHOD FOR LAYING A ROAD MAT ON A VERTICALLY CURVED ROAD BED WITH AROAD MACHINE WHICH IS EQUIPPED WITH A ROAD MAT LEVELING MEMBER AND WITHMEANS FOR ADJUSTING SAID MEMBER VERTICALLY TO CONTROL THE THICKNESS OFSAID MAT AND THE LOCATION OF ITS UPPER SURFACE, SAID METHOD COMPRISINGPROVIDING AN OPTICAL LINE OF REFERENCE EXTENDING PARALLEL TO THE CHORDOF AN ARCUATE PORTION OF SAID ROAD BED, MOVING A CONTROLLING MEMBER,WHICH IS MOUNTED ON SAID LEVELING MEMBER AND WHICH HAS A CONTROLLINGCURVED SURFACE, THE ORDINATES OF WHICH REPRESENT THE VERTICAL CONTOUR OFSAID ARCUATE PORTION, PAST A VERTICAL PLANE CONTAINING SAID REFERENCELINE AT A RATE PROPORTIONAL TO THE RATE OF TRAVEL OF THE MACHINE ALONGTHE ROAD, AND MOVING SAID LEVELING MEMBER UP OR DOWN AS REQUIRED TOCAUSE SUCCESSIVE POINTS ON SAID CURVED SURFACE TO LIE ON SAID REFERENCELINE AS THE MACHINE TRAVELS ALONG THE ROAD.